The present invention relates to a control device of a powertrain of a vehicle or the like, particularly to a control device of a powertrain with a centrifugal pendulum damper.
Conventionally, the use of an engine cylinder cut-off operation and homogenous charge-compression ignition (HCCI) combustion, and furthermore, of an art such as making an automatic transmission torque converter-less by eliminating the torque converter, are known for increasing fuel efficiency of a vehicle equipped with a powertrain comprising a power transmission path which extends from an engine to a drive wheel via an automatic transmission.
However, there is a tendency for output torque fluctuations to become larger in an engine which has adopted a cylinder cut-off operation or HCCI combustion, and also, because engine torque fluctuations are output from an automatic transmission without attenuation when the automatic transmission has been made torque converter-less, torque fluctuations transmitted to a power transmission system on an automatic transmission output side become larger in a vehicle using such an art. In particular, torsional vibrations caused by these larger torque fluctuations may become a cause of vibration or noise generation in various vehicle parts if amplified by resonance of the power transmission system.
For the sake of convenience, the term “automatic transmission” will hereinafter be described as including not only a multi-stage automatic transmission provided with a transmission mechanism for switching between gear ratios in a step-wise manner, but as also including a continuously variable automatic transmission (CVT) provided with a transmission mechanism for continuously changing gear ratios as well. Additionally, a transmission mechanism which is an automatic transmission does not include a torque converter or a torsion damping mechanism.
With respect to the above-described problem, an art is known such as, for example, operatively coupling a centrifugal pendulum damper to a power transmission shaft as disclosed in JP2014228009A. The centrifugal pendulum damper has a support member which rotates together with the power transmission shaft, and a pendulum which is a mass supported by the member so as to be able to swing centered on a circumferential point at a fixed radius from an axial center of the support member. When the pendulum swings due to torque fluctuations, a circumferentially-directed component of force is generated in the support member which receives the centrifugal force acting on the pendulum. This component of force acts as an anti-torque which suppresses torque fluctuations of the support member and the power transmission shaft.
In an engine low-speed rotation range, such as at a time of starting, the centrifugal pendulum damper coupled to the power transmission shaft also rotates at a low speed and the centrifugal force acting on the pendulum is reduced, and due to this reduced centrifugal force, a torque fluctuation suppression operation of the pendulum becomes unstable and the pendulum may cause generation of abnormal noise due to contact with a peripheral member. In the invention of JP2014228009A, a connection/disconnection mechanism for attenuating power transmission to the centrifugal pendulum damper is provided between the power transmission shaft and the centrifugal pendulum damper to suppress generation of abnormal noise. As described below, a connection/disconnection mechanism of the present invention is a frictionally-engaged type of clutch which transmits power by frictional force and which can smoothly transmit torque, even when there is a difference in rotational speeds between an input shaft and an output shaft, by shifting from a released state to a slip state or an engaged state while adjusting an engagement degree by controlling hydraulic pressure, electric current, or the like. In the present invention, “engaged” and “released” denote that the connection/disconnection mechanism as a whole is connected and cut-off, respectively, and “slipping” denotes an incomplete connection in which the connection/disconnection mechanism is slipping.
However, as in the prior art described in JP2014228009A, when the connection/disconnection mechanism is disposed between the power transmission shaft and the centrifugal pendulum damper, and a connected state of the connection/disconnection mechanism is maintained even during an engine high-speed rotation range in order to suppress torque fluctuations, a rotational speed of the centrifugal pendulum damper connected via the connection/disconnection mechanism is also increased, and there is a possibility that over-rotation may degrade reliability of the centrifugal pendulum damper due to over-rotation of the damper.